The Division of Immunology provides flow cytometry services to other divisions at NERPRC, especially with regards to AIDS related research projects carried out in the Division of Microbiology and Pathology. Supported by a supplemental grant from the Office of AIDS Research, NIAID, the facility was renovated in 1994 to include a Becton Dickinson FACScan, which provides routine three-color immunophenotyping, and a Becton Dickinson Vantage, which can perform four and five-color analysis and cell sorting. In addition to routine immunophenotyping performed on SIV-infected animals, projects outside the Division of Immunology supported by the Flow Cytometry Facility include 1) Pathogenesis of acute SIV infection (Pathology) 2) Alterations in gastrointestinal lymphoid tissue induced by SIV infection (Pathology) 3) Acute infection with rhesus EBV (F. Wang, Brigham and Women's Hospital) 4) Detection of SIV infection using reporter genes (Microbiology) 5) Functional effects of EBV proteins on surface antigen expression (F. Wang, Brigham and Women's Hospital) 6) Characterization of a novel population of hematopoietic stem cells (Mulligan, Goodell, MIT) 7) Routine CD4+ T cell level determinations (NERPRC- Microbiology, Pathology, Immunology) 8) Analysis of the functional effects of SIV nef on surface CD4 expression (Microbiology) 9) The role of CD1 in AIDS pathogenesis (Brenner, Brigham and Women's Hospital) 10) Effects of M. avium infection of surface antigen expression in rhesus monocytes (Pathology). 11) Effects of HIV infection on surface MHC expression (R. P. Johnson, NERPRC Immunology & O. Yang, Mass General Hospital). Over 20,000 samples were processed in the preceding 12 months. If we compare our costs to an outside lab, this translates to a savings of $150,000. In addition, we have produced a number of antibodies in house, using the Cellco culture system. With an expenditure of $24,648 we have generated a stock of both conjugated and unconjugated antibodies that translates to a commercial value of $271,292. This will obviously provide a substantial savings on reagents over the next 5 years. In addition, we have made "in house" reagents available for routine CD4 immunophenotyping at NERPRC; as well as to other departments for use in studies requiring FACS analysis. Unique reagents (anti-CD3) have been made freely available. We have also provided reagents to 1) N. Letvin, K. Reimann, Beth Israel Hospital 2) J. Zimmerberg, National Institutes of Health 3) Stem Cell Technologies, Canada 4) F. Wang, Brigham and Women's Hospital 5) D. Scadden, Mass General Hospital 6) M. Cromwell, Genetics Institute 7) J. Heeney, Biomedical Primate Research Center, The Netherlands In addition, our laboratory responds to numerous questions regarding the immunophenotyping of rhesus macaque blood and bone marrow.